Shortly after the start of the civil war in 2011, the Obama administration placed sanctions against Syria and supported the Free Syrian Army rebel faction by covertly authorizing Timber Sycamore under which the Central Intelligence Agency (CIA) armed and trained rebels. Following the Islamic State's occupation of Eastern Syria in August 2014, the United States conducted surveillance flights in Syria to gather intelligence regarding the Islamic State. In September 2014, the United States-led coalition—which involves the United Kingdom, France, Jordan, Turkey, Canada, Australia, and others—launched an air campaign against the Islamic State and al-Nusra Front inside Syria.


The US missile strike on Shayrat Airbase on 7 April 2017 was the first time the US deliberately attacked Syrian government forces during the war,^[165] and marked the start of a series of direct military actions by US forces against the Syrian government and its allies via airstrikes and aircraft shoot-downs, mainly in defense of either the Syrian Democratic Forces or the Syrian Free Army opposition group based in al-Tanf. In mid-January 2018, the Trump administration indicated its intention to maintain an open-ended military presence in Syria to accomplish US political objectives, including countering Iranian influence and ousting Syrian president Bashar al-Assad.^[166][167] However, on 19 December, President Trump unilaterally ordered the withdrawal of the 2,000–2,500 US ground troops in Syria at the time, which was to be completed in 2019.^{[168][169][170]} With proliferating concerns over a potential power vacuum, the US announced on 22 February 2019 that instead of a total withdrawal, a contingency force of around 400 US troops would remain garrisoned in Syria indefinitely, and that their withdrawal would be gradual and conditions-based, returning to a policy of open-ended American military presence in the country.^[171][172]


In 2019, the coalition saw decisive results in its intervention against the Islamic State; the terror group lost its last remaining territory in Syria during the battle of Baghuz Fawqani^[173] and its leader Abu Bakr al-Baghdadi died during a US special forces raid in Idlib in October 2019.^[174] The Trump administration ordered all US forces to withdraw from Rojava in early October ahead of a Turkish incursion into the region, a controversial move widely seen as a reneging of the US's alliance with the SDF in favor of NATO ally Turkey.^[175] However, by November 2019, US troops instead repositioned to eastern Syria, reinforcing their presence in the al-Hasakah and Deir ez-Zor governorates, with the subordinate mission of securing SDF-controlled oil and gas infrastructure from the IS insurgency and the Syrian government.^[176] On 23 November 2019, the head of US Central Command stated there was no "end date" on the US's intervention in Syria.^[177]


As of February 2021, there are around 900 US soldiers operating in Syria, according to the US Department of Defense.^[47][178]